New Chromenylium−cyanine based dual channel chemosensors for copper and hypochlorite sensing

Based on a change in optical properties of chromenylium−cyanine Schiff base derivatives (5a-c), a series of colorimetric dual sensors have been for the first time designed, synthesized and characterized to monitor Cu²⁺ and OCl⁻ ions at near-IR (NIR) region in aqueous samples. The colorimetric responses of the sensors toward Cu²⁺ and OCl⁻ ions were evaluated for aqueous samples within a series of the competitive anions and cations at pH 7.2. The sensors detected Cu²⁺ selectively via Cu²⁺-promoted spirocyclic ring–opening reaction while photophysical change during OCl⁻ recognition is due to the spirocyclic ring−opening reaction by coordination Cu²⁺ ion generated from reaction between Cu⁺ and hypochlorite ions in analysis media. Mass and IR data suggest a 1:1 complex formation between Cu²⁺ and the receptor via phenolic O atom, N atom from Schiff base and O atom from spirocycle form. The detection limits of the dual sensors (5a-c) were determined to be 3.3 × 10⁻⁸ M, 1.93 × 10⁻⁸ M and 2.36 × 10⁻⁸ for Cu²⁺ determination and 2.83 × 10⁻⁸ M, 2.10 × 10⁻⁸ M and 2.60 × 10⁻⁸ M for OCl⁻ determination, indicating a high sensitivity of the sensors for Cu²⁺ and OCl⁻ detection Additionally, we present the first single-crystal structure analysis of a chromenylium-cyanine Schiff base in this study.